Quantitative analysis of six pesticides in fruits by capillary electrophoresis‐electrospray‐mass spectrometry

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Abstract
A method to identify and quantify six pesticide residues – dinoseb, pirimicarb, procymidone, pyrifenox, pyrimethanil, and thiabendazole – in peaches and nectarines using capillary electrophoresis‐electrospray ionization‐quadrupole ion trap‐tandem mass spectrometry (CE‐ESI‐MS/MS) is described. Separation was carried out using a buffer of 0.3 M ammonium acetate at pH 4 with 10% methanol. Pesticide residues present in peach and nectarine samples were preconcentrated by solid‐phase extraction using C18, eluted with CH2Cl2, concentrated to dryness, and redissolved in buffer to obtain lower detection limits. The recoveries of the analytes ranged from 58 to 99% and the relative standard deviations were 9 to 19%. Under optimized CE‐MS/MS conditions the minimum detectable levels for the six pesticides in spiked peach samples were between 0.01 mg/kg for pirimicarb and 0.05 mg/kg for procymidone with pressure injection of 50 mbar for 5 s (5 nL) at a signal‐to‐noise ratio of 3, which constitutes a severalfold increase in sensitivity compared to CE‐MS, using a single quadrupole, and to conventional CE‐UV. The potential of the method was demonstrated by analyzing different samples taken from regional agricultural cooperatives. The pesticides most often detected were thiabendazole and procymidone.